With the development of aerospace technology, more and more spacecrafts carry large flexible mechanisms such as solar panels and antennas, and these flexible mechanisms make the functions of the spacecrafts stronger and stronger, but meanwhile bring along a challenge for the attitude control of the spacecrafts, especially when the spacecrafts have a high requirement for control accuracy, for example earth observation satellites, space telescopes and so on. Therefore, a flexible spacecraft will not only suffer from external environmental disturbance, but also suffer from severe influence from rigid-flexible coupling dynamics when it operates in the space. With regards to such complicated problems, many scholars have proposed corresponding control methods, among which H∞ control, sliding-mode structure control and the like are very common. However, H∞ control is a typical disturbance suppression method, and it considers all disturbances as single norm-bounded disturbances, thus resulting in a low control accuracy. While the sliding-mode structure control has advantages such as robustness, rapidity and so on, but its control rate is generally very complicated, and has chattering phenomenon, and thus is not beneficial to practical industrial application. Moreover, most of the attitude control methods currently design a controller by assuming that all states of the system are measurable. However, it is difficult to satisfy the above assumption in the practical aerospace engineering, for example, in a case where some of the measurement sensors are faulted. Further, due to the reasons such as the cost of measurement of angular velocity and the like, more and more scholars begin to study the attitude control issue without the measurement of angular velocity, which actually is also an attitude control issue based output feedback. Therefore, it has theoretically and practically meaningful to design an attitude controller with high accuracy based on output feedback. The early work also involves estimating the disturbance caused by rigid-flexible coupling by using DOBC, but the premise is that all state variables of the system are assumed to be measurable, and the change rate of the disturbance is bounded.
Control based on a disturbance observer (DOBC) makes full use of the characteristic of disturbance, and achieves high-accuracy estimation and compensation of disturbance, and can be easily combined with other control methods. Therefore, a refined compound attitude controller can be configured based on a disturbance observer to realize both compensation and suppression of disturbance, thereby improving the attitude control accuracy of a flexible spacecraft.
Accordingly, there is a need for a method for refined attitude control based on output feedback for a flexible spacecraft that can efficiently compensate for the rigid-flexible coupling disturbance and suppress external environmental disturbance.